A Disk-driven Resonance as the Origin of High Inclinations of Close-in Planets
A Disk-driven Resonance as the Origin of High Inclinations of Close-in Planets
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DOI：
10.3847/2041-8213/abb952
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发表时间：
2020-08
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影响因子：
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通讯作者：
C. Petrovich;D. Muñoz;K. Kratter;R. Malhotra
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文献类型：
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作者：
C. Petrovich;D. Muñoz;K. Kratter;R. Malhotra
最近对过境近距离行星的描述揭示了一个有趣的亚海王星种群，它们的轨道相对于其宿主星星的赤道高度倾斜，甚至是极地轨道。任何关于这些近极行星起源的可行理论都必须解释：（1）观测到的恒星偏心率，（2）相当大的偏心率，（3）具有大倾角的木星伴星的存在。在这项工作中，我们提出了一个满足这些要求的理论模型，而无需调用潮汐耗散或大的原始倾向。相反，在行星形成的后期，原行星盘的分散促进了倾斜，引发了共振扫描和参数不稳定的过程。该机制包括两个步骤。首先，一个节点的长期共振激发倾角大的值，然后，一旦倾角达到临界值，线性偏心不稳定性被触发，失谐的共振和结束倾角增长。临界倾角被广义相对论的进动推到很高的值，使极轨道成为一个固有的后牛顿结果。我们的模型预测，极地，近距离的亚海王星共存于低恒星轨道的冷彗星。
The recent characterization of transiting close-in planets has revealed an intriguing population of sub-Neptunes with highly tilted and even polar orbits relative to their host star’s equator. Any viable theory for the origin of these close-in, polar planets must explain (1) the observed stellar obliquities, (2) the substantial eccentricities, and (3) the existence of Jovian companions with large mutual inclinations. In this work, we propose a theoretical model that satisfies these requirements without invoking tidal dissipation or large primordial inclinations. Instead, tilting is facilitated by the protoplanetary disk dispersal during the late stage of planet formation, initiating a process of resonance sweeping and parametric instability. This mechanism consists of two steps. First, a nodal secular resonance excites the inclination to large values; then, once the inclination reaches a critical value, a linear eccentric instability is triggered, which detunes the resonance and ends inclination growth. The critical inclination is pushed to high values by general relativistic precession, making polar orbits an inherently post-Newtonian outcome. Our model predicts that polar, close-in sub-Neptunes coexist with cold Jupiters in low stellar obliquity orbits.